1. Field of the Invention
The present invention relates to electrical connectors and more particularly to electrical connectors including means for controlling electrical cross talk and impedance.
2. Brief Description of Prior Developments
As the density of interconnects increases and the pitch between contacts approaches 0.025 inches or 0.5 mm, the close proximity of the contacts increases the likelihood of strong electrical cross talk coupling between the contacts. In addition, maintaining design control over the electrical characteristic impedance of the contacts becomes increasingly difficult. In most interconnects, the mated plug/receptacle contact is surrounded by structural plastic with air spaces to provide mechanical clearances for the contact beam. As is disclosed in U.S. Pat. No. 5,046,960 to Fedder, these air spaces can be used to provide some control over the characteristic impedance of the mated contact. Heretofore, however, these air spaces have not been used, in conjunction with the plastic geometry, to control both impedance and, more importantly, cross talk.
In the connector of the present invention there is a first member and a second member each of which comprises a metallic contact means and a dielectric base means. On each member the metallic contact means extends perpendicularly from the dielectric base means. The two metallic contact means connect to form what is referred to herein as a generally xe2x80x9cI-beamxe2x80x9d shaped geometry. The concept behind the I-beam geometry is the use of strong dielectric loading through the structural dielectric to ground on the top and bottom of the mated contact edges and a relatively light loading through air on the mated contact sides. These different dielectric loadings are balanced in such a way as to maintain a controlled impedance and yet minimize coupling (and cross talk) between adjacent contacts. In this way, all lines of the interconnect can be dedicated to signals while maintaining a controlled impedance and a relatively low rise time-cross talk product of less than 1 nano-second percent. Typical rise time-cross talk values for existing 0.05 to 0.025 inch pitch controlled impedance interconnects range from 2.5 to 4 nano-second percent.
The I-beam geometry of this invention may also be advantageously used in an electrical cable assembly. In such an assembly a control support dielectrical web element is perpendicularly interposed between opposed flange elements. Each of the flange elements extend perpendicularly away from the terminal ends of the web element. On both of the opposed sides of the web there is a metalized signal line. The opposed end surfaces of the flanges are metalized to form a ground plane. Two or more such cable assemblies may be used together such that the flanges are in end to end abutting relation and the longitudinal axes of the conductive elements are parallel. An insulative jacket may also be positioned around the entire assembly.